Recently, there is an increasing need for an object recognition technology for detecting an object, based on information measured by a measurement device. The measurement device is mounted on, for example, a car and is used for automatically recognizing an object (pedestrian or the like) existing in a travel direction of a car.
A monitoring camera, a distance sensor, a laser radar, an infrared tag, and the like are frequently used as a measurement device. Then, if introduction cost for newly installing the measurement device is not required and an existing measurement device can be used, it is possible to introduce an object recognition technology with lower cost. For this reason, development of a technology is underway in which an existing monitoring camera is used as a measurement device and an object is detected based on an image acquired from the monitoring camera. Then, as a technology for recognizing an object from an image, for example, a method of searching whether or not a portion similar to sample data exists in an image in a state where lots of sample data (sample images) of an object to be recognized is stored in a database in advance is generally used.
However, in a case where appearance of the object differs greatly from the sample data due to illumination conditions or the like, it is difficult to recognize an object by this method. Therefore, attention is paid to a technology for recognizing an object with high accuracy by capturing an image of an object using a plurality of cameras and measuring a three-dimensional shape of the object. For example, an object recognition technology which uses a stereo camera is used as such a technology. In this technology, a distance in a real space from the stereo camera to the object is calculated for each pixel of the image by using a parallax calculated by comparing a pair of left and right camera images captured by the stereo camera. Then, the object is recognized from the image by using three-dimensional information of the object measured based on the calculated distance information.
For example, PTL 1 is cited as an object recognition technology which uses a stereo camera. PTL 1 discloses that “an obstacle closer to a prescribed distance is recognized based on parallax information of the stereo camera and an obstacle farther than the prescribed distance is recognized by using pattern recognition”.